exception error when I add [Required] to class

I get an exception when I add [Required] to class:

An exception of type 'System.InvalidOperationException' occurred in EntityFramework.dll but was not handled in user code.

Additional information: The model backing the 'MovieDBContext' context has changed since the database was created. Consider using Code First Migrations to update the database."

The class

public class Movie
{
    public int ID { get; set; }

    [StringLength(60, MinimumLength = 3)]
    [Required]
    public string Title { get; set; }

    [Display(Name = "Release Date"), DataType(DataType.Date)]
    [Range(typeof(DateTime), "1/1/1966", "1/1/2020")]
    public DateTime ReleaseDate { get; set; }

    [Required]
    [StringLength(30)]
    public string Genre { get; set; }

    [Range(1, 100),DataType(DataType.Currency)]
    public decimal Price { get; set; }

    [StringLength(5)]
    public string Rating { get; set; }
}

public class MovieDBContext : DbContext
{
    public DbSet<Movie> Movies { get; set; }
}

Controller

namespace ICmovie.Controllers
{
    public class MoviesController : Controller
    {
        private MovieDBContext db = new MovieDBContext();

        // GET: Movies
        public ActionResult Index(string movieGenre, string searchString)
        {
            var GenreLst = new List<string>();

            var GenreQry = from d in db.Movies
                           orderby d.Genre
                           select d.Genre;

            GenreLst.AddRange(GenreQry.Distinct());
            ViewBag.movieGenre = new SelectList(GenreLst);

            var movies = from m in db.Movies
                         select m;

            if (!String.IsNullOrEmpty(searchString))
            {
                movies = movies.Where(s => s.Title.Contains(searchString));
            }

            if (!string.IsNullOrEmpty(movieGenre))
            {
                movies = movies.Where(x => x.Genre == movieGenre);
            }

            return View(movies);
        }

        // GET: Movies/Details/5
        public ActionResult Details(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }

            Movie movie = db.Movies.Find(id);

            if (movie == null)
            {
                return HttpNotFound();
            }

            return View(movie);
        }

        // GET: Movies/Create
        public ActionResult Create()
        {
            return View();
        }

        // POST: Movies/Create
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
        // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Create([Bind(Include = "ID,Title,ReleaseDate,Genre,Price,Rating")] Movie movie)
        {
            if (ModelState.IsValid)
            {
                db.Movies.Add(movie);
                db.SaveChanges();
                return RedirectToAction("Index");
            }

            return View(movie);
        }

        // GET: Movies/Edit/5
        public ActionResult Edit(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }

            Movie movie = db.Movies.Find(id);

            if (movie == null)
            {
                return HttpNotFound();
            }

            return View(movie);
        }

        // POST: Movies/Edit/5
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
        // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Edit([Bind(Include = "ID,Title,ReleaseDate,Genre,Price,Rating")] Movie movie)
        {
            if (ModelState.IsValid)
            {
                db.Entry(movie).State = EntityState.Modified;
                db.SaveChanges();
                return RedirectToAction("Index");
            }

            return View(movie);
        }

        // GET: Movies/Delete/5
        public ActionResult Delete(FormCollection fcNotUsed, int id = 0)
        {
            Movie movie = db.Movies.Find(id);

            if (movie == null)
            {
                return HttpNotFound();
            }

            db.Movies.Remove(movie);
            db.SaveChanges();

            return RedirectToAction("Index");
        }

        // POST: Movies/Delete/5
        [HttpPost, ActionName("Delete")]
        [ValidateAntiForgeryToken]
        public ActionResult DeleteConfirmed(int id)
        {
            Movie movie = db.Movies.Find(id);
            db.Movies.Remove(movie);
            db.SaveChanges();
            return RedirectToAction("Index");
        }

        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                db.Dispose();
            }
            base.Dispose(disposing);
        }
    }
}